There is presently an increased development of large, multi-partite systems for performing complex overall functions. Within increased complexity of the equipment has also come increased complexity in the steps of maintaining, servicing, and trouble shooting the equipment, and hence increased difficulty in training personnel for these functions. The practice has developed of creating at a training center a "simulator," that is, a structure having the physical appearance of the equipment to be serviced, and programming a computer with the steps of maintenance procedures. The simulator need not be capable of actually performing the functions of the equipment it simulates, but simply presents outputs, at identifiable terminals, which are identical with those which would be supplied by the equipment itself. Also provided are probes simulating those of volt meters, signal generators, oscilloscopes, and similar test equipment.
It is desirable that the computer be able not only to program the desired actions of the person being trained, but also to determine whether the intended step is in fact being performed. Thus, if the maintenance step is to check the voltage at the input to a particular unit, it is necessary to determine that the trainee using the simulator has selected the probe of a volt meter, and has applied it to the correct terminal.